deno.land / std@0.166.0 / encoding / csv.ts
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// This module is browser compatible.
/** Port of the Go * [encoding/csv](https://github.com/golang/go/blob/go1.12.5/src/encoding/csv/) * library. * * @module */
import { assert } from "../_util/asserts.ts";import type { ReadOptions } from "./csv/_io.ts";import { Parser } from "./csv/_parser.ts";
export { ERR_BARE_QUOTE, ERR_FIELD_COUNT, ERR_INVALID_DELIM, ERR_QUOTE, ParseError,} from "./csv/_io.ts";export type { ReadOptions } from "./csv/_io.ts";
const QUOTE = '"';export const NEWLINE = "\r\n";
export class StringifyError extends Error { override readonly name = "StringifyError";}
function getEscapedString(value: unknown, sep: string): string { if (value === undefined || value === null) return ""; let str = "";
if (typeof value === "object") str = JSON.stringify(value); else str = String(value);
// Is regex.test more performant here? If so, how to dynamically create? // https://stackoverflow.com/questions/3561493/ if (str.includes(sep) || str.includes(NEWLINE) || str.includes(QUOTE)) { return `${QUOTE}${str.replaceAll(QUOTE, `${QUOTE}${QUOTE}`)}${QUOTE}`; }
return str;}
type PropertyAccessor = number | string;
/** * @param header Explicit column header name. If omitted, * the (final) property accessor is used for this value. * * @param prop Property accessor(s) used to access the value on the object */export type ColumnDetails = { header?: string; prop: PropertyAccessor | PropertyAccessor[];};
export type Column = ColumnDetails | PropertyAccessor | PropertyAccessor[];
type NormalizedColumn = Omit<ColumnDetails, "header" | "prop"> & { header: string; prop: PropertyAccessor[];};
function normalizeColumn(column: Column): NormalizedColumn { let header: NormalizedColumn["header"], prop: NormalizedColumn["prop"];
if (typeof column === "object") { if (Array.isArray(column)) { header = String(column[column.length - 1]); prop = column; } else { prop = Array.isArray(column.prop) ? column.prop : [column.prop]; header = typeof column.header === "string" ? column.header : String(prop[prop.length - 1]); } } else { header = String(column); prop = [column]; }
return { header, prop };}
type ObjectWithStringPropertyKeys = Record<string, unknown>;
/** An object (plain or array) */export type DataItem = ObjectWithStringPropertyKeys | unknown[];
/** * Returns an array of values from an object using the property accessors * (and optional transform function) in each column */function getValuesFromItem( item: DataItem, normalizedColumns: NormalizedColumn[],): unknown[] { const values: unknown[] = [];
if (normalizedColumns.length) { for (const column of normalizedColumns) { let value: unknown = item;
for (const prop of column.prop) { if (typeof value !== "object" || value === null) continue; if (Array.isArray(value)) { if (typeof prop === "number") value = value[prop]; else { throw new StringifyError( 'Property accessor is not of type "number"', ); } } // I think this assertion is safe. Confirm? else value = (value as ObjectWithStringPropertyKeys)[prop]; }
values.push(value); } } else { if (Array.isArray(item)) { values.push(...item); } else if (typeof item === "object") { throw new StringifyError( "No property accessor function was provided for object", ); } else { values.push(item); } }
return values;}
/** * @param headers Whether or not to include the row of headers. * Default: `true` * * @param separator Delimiter used to separate values. Examples: * - `","` _comma_ (Default) * - `"\t"` _tab_ * - `"|"` _pipe_ * - etc. */export type StringifyOptions = { headers?: boolean; separator?: string; columns?: Column[];};
/** * @param data The array of objects to encode * @param options Output formatting options */export function stringify( data: DataItem[], { headers = true, separator: sep = ",", columns = [] }: StringifyOptions = {},): string { if (sep.includes(QUOTE) || sep.includes(NEWLINE)) { const message = [ "Separator cannot include the following strings:", ' - U+0022: Quotation mark (")', " - U+000D U+000A: Carriage Return + Line Feed (\\r\\n)", ].join("\n"); throw new StringifyError(message); }
const normalizedColumns = columns.map(normalizeColumn); let output = "";
if (headers) { output += normalizedColumns .map((column) => getEscapedString(column.header, sep)) .join(sep); output += NEWLINE; }
for (const item of data) { const values = getValuesFromItem(item, normalizedColumns); output += values .map((value) => getEscapedString(value, sep)) .join(sep); output += NEWLINE; }
return output;}
export interface ParseOptions extends ReadOptions { /** * If you provide `skipFirstRow: true` and `columns`, the first line will be skipped. * If you provide `skipFirstRow: true` but not `columns`, the first line will be skipped and used as header definitions. */ skipFirstRow?: boolean;
/** * If you provide `string[]` or `ColumnOptions[]`, those names will be used for header definition. */ columns?: string[];}
/** * Csv parse helper to manipulate data. * Provides an auto/custom mapper for columns. * @param input Input to parse. * @param opt options of the parser. * @returns If you don't provide `opt.skipFirstRow` and `opt.columns`, it returns `string[][]`. * If you provide `opt.skipFirstRow` or `opt.columns`, it returns `Record<string, unkown>[]`. */export function parse( input: string,): string[][];export function parse( input: string, opt: Omit<ParseOptions, "columns" | "skipFirstRow">,): string[][];export function parse( input: string, opt: Omit<ParseOptions, "columns"> & { columns: string[]; },): Record<string, unknown>[];export function parse( input: string, opt: Omit<ParseOptions, "skipFirstRow"> & { skipFirstRow: true; },): Record<string, unknown>[];export function parse( input: string, opt: ParseOptions,): string[][] | Record<string, unknown>[];export function parse( input: string, opt: ParseOptions = { skipFirstRow: false, },): string[][] | Record<string, unknown>[] { const parser = new Parser(opt); const r = parser.parse(input);
if (opt.skipFirstRow || opt.columns) { let headers: string[] = []; let i = 0;
if (opt.skipFirstRow) { const head = r.shift(); assert(head != null); headers = head; i++; }
if (opt.columns) { headers = opt.columns; }
return r.map((e) => { if (e.length !== headers.length) { throw new Error( `Error number of fields line: ${i}\nNumber of fields found: ${headers.length}\nExpected number of fields: ${e.length}`, ); } i++; const out: Record<string, unknown> = {}; for (let j = 0; j < e.length; j++) { out[headers[j]] = e[j]; } return out; }); } return r;}
std
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